The invention concerns an apparatus for the determination of microorganisms in liquid test specimens, including a specimen providing station with a transport apparatus for the continuous presentation of cuvettes containing specimens to be investigated, a dosing station with a pipetting apparatus for removing specimens from the cuvettes and for filling the specimens into measuring chambers formed in a measuring chamber plate in matrix arrangement, and a measuring station with a measuring apparatus for optically measuring the specimens in the measuring chambers.
In order to be able to detect, for example, bacteria in liquid test specimens with an apparatus of the previously mentioned kind, one proceeds as follows. The measuring chambers of the measuring chamber plate, a so-called microtitration plate, are filled with a culturing solution and/or detection chemicals for certain bacteria. A specimen is distributed to a number of chambers. With the help of the measuring device, it is tested whether the absorption behavior of the solution in the measuring chambers changes, especially whether a color reaction appears because of the detection chemicals. If this is not the case, the measuring chamber plate is placed in an oven to produce a multiplication of the bacteria in the individual measuring chambers. The above-mentioned steps must be repeated many times during a time period of from six to eight hours. This means that the measuring chamber plate has to be taken out of the oven by means of a grasping system and moved to the dosing unit, the measuring unit, and finally back into the oven. This is time consuming and requires not only a high mechanical expense but also much space for the storage of the measuring chamber plates. If an error appears in the mechanical handling which is not immediately noted, the process because of its long duration often cannot be started again until the next work day.
The invention has as its object, to simplify the manipulation of the measuring chamber plates and thereby to avoid sources of error, as well as to reduce the space requirement of the apparatus.
These objects are solved by an apparatus of the previously mentioned kind and in accordance with the invention by an endless conveyor which is formed to serially receive the measuring chamber plates and to transport the same through the dosing station, the measuring station and through a temperature controllable waiting zone.
In the solution of the invention, the measuring chamber plates remain connected with the endless conveyor during the entire duration of the investigation. The grasping apparatus required by the state of the art for the manipulation of the measuring chamber plates can be eliminated. Thus, the technical expense is lowered and also so is the space requirement for the apparatus of the invention. Since the previously required manipulation procedure offered an abundance of error sources, the apparatus of the invention in operation is also essentially more functionally reliable than customary apparatuses of this kind.
Preferably, the endless conveyor has a plurality of carrier frames each having at least one receiving compartment for a measuring chamber plate. Therefore, the measuring chamber plates can in a simple way be connected with the endless conveyor, insofar as each is simply inserted or pushed into a receiving compartment.
The endless conveyor preferably has an endless conveying member, for example, a belt or chain, which is guided over rolls and to which the carrier frames are fastened. To save space, or with the same space allotment to increase the storage capacity for the measuring chamber plates, the conveyor member can run in at least two vertically superimposed planes. This can be achieved in a simple way in that at two horizontally spaced locations at least two belt rolls are arranged axially over one another, and that at least a further direction changing roll is provided for the conveyor member which has a location outside of a connecting line between the first mentioned belt roll locations. In this way, the carrier frames fastened to the conveyor member can change from one plane to the other without obstructing one another.
The use of so-called microtitration plates in which the measuring chambers each have a very small volume requires an exact positioning of the measuring chamber plates in the optical measuring apparatus. To achieve this, it is advantageous if guide means are provided at the measuring station for guiding the carrier frames relative to the measuring apparatus. Thereby the measuring chamber plates can be positioned exactly with respect to the measuring optic system despite the flexibility of the conveyor member.
In a preferred embodiment the guide means include guide rolls arranged on both sides of the transport path of the carrier frames and which come into engagement with the side edges of the carrier frames running parallel to the transport direction. To on one hand make possible a jolt-free introduction of the carrier frames between the guide rolls and on the other hand to assure an exact positioning, it is advantageous if the guide roll intended for engagement with one of the side faces is biased in the direction toward to the oppositely lying guide roll. Thereby a play-free engagement of the guide rolls onto the side surfaces of the carrier frame is assured.
In order to avoid not only sideways deflection but also movement of the measuring chamber plates in the vertical direction inside of the measuring station, it is proposed that guide grooves are formed in the side surfaces of the carrier frames running parallel to the transport direction, which grooves receive corresponding portions of the guide rolls. The centering of the carrier frames at the measuring station can, in this case, be further improved if the guide grooves and/or the guide rolls in their edge areas have a V-profile.
The receiving compartment of the carrier frame is preferably formed as a sliding guide with an opening lying at the side of the carrier frame remote from the conveyor member. Because of this, the measuring chamber plates can be pushed into the associated receiving compartments by a simple pushing mechanism at the dosing station and can also be likewise easily removed.
Since the measuring chamber plates remain in the carrier frames during the entire investigation procedure and are also measured while in the carrier frames, it is advantageous if the carrier frames either have entirely no bottoms or if the bottom of the receiving compartment at least in the region of the measuring chambers of a measuring chamber plate inserted into the receiving compartment is transparent. This can occur either in that a transparent plate is so printed that measuring areas only remain free at the desired spots or in that the bottom of the receiving compartment at the spots corresponding to the measuring chambers of a measuring chamber plate inserted into the measuring compartment has passthrough openings.
To simplify the automatic delivery of the measuring chamber plates for the inoculation, it is advantageous if at the dosing station, at least one magazine pocket is provided for the storage of measuring chamber plates stacked upon one another and if a delivery device is also provided for delivering the uppermost or lowermost measuring chamber plate of the stack from the magazine pocket to a receiving compartment of a carrier frame moving past the dosing station. Also, in the case of this solution, no complicated grasping system is needed. It is sufficient to have a simple pusher for removing the measuring chamber plate from the magazine. If the magazine pocket is located below the delivery surface for the insertion of a measuring chamber plate into a receiving compartment, it is advantageous if, in the magazine pocket, an upwardly biased bottom plate is arranged so that the entire measuring chamber plate stack is always pushed against an upper stop.
The delivery mechanism for delivery of the measuring chamber plates is preferably so formed and controlled that a measuring chamber plate removed from the magazine pocket is positioned at a dosing position at which the specimen material is filled into the measuring chambers and subsequently, the measuring chamber plate is delivered to the receiving compartment of a carrier frame. This positioning movement can be carried out by one simple pusher.
Since one and the same specimen as a rule is investigated in respect to different bacteria, in the measuring plate at least one group of measuring chambers is formed which are connected with at least one filling opening and with one another by capillaries. This gives the possibility of filling all of the measuring chambers with one single filling procedure. The filling opening for this simple filling can be formed relatively large. The measuring chambers, however, need to have only very small volumes. This reduces not only the space requirement for the individual measuring chamber plates, but reduces above all also the volume of specimen that has to be supplied and also after the completion of the investigation, of the appearing waste which often has to be taken care of as special waste.
Preferably, in each measuring chamber plate, the measuring chambers are arranged in rows and columns with the measuring chambers lying in one row being connected by capillaries and with the filling openings of the rows being arranged in a column. This again simplifies the automatic filling of the specimens by means of the pipetting apparatus.
Preferably the column of filling openings is arranged at an end of the measuring chamber plate with respect to the insertion direction and extends perpendicularly to the insertion direction, with the carrier frame being provided with a cover which closes the filling openings of a measuring chamber plate inserted into a receiving compartment. Thereby since the measuring chambers as well as the filling openings are covered, it is assured that during the movement of the measuring chamber plates by the endless conveyor no material can be deflected out of the measuring chambers nor can any foreign material get into the measuring chambers.
To assure that the specimen liquid also arrives into the last measuring chamber of a measuring chamber row, it is advantageous if at the end of a row of connected together measuring chambers, an air receiving hollow space is arranged.
To be able to achieve the reception in all of the measuring chambers of exactly the same amount of liquid, in the capillary between each two measuring chambers a cross-sectional change is formed which prevents the automatic passage of liquid by capillary effect and which prevention of capillary effect can be removed by exerting an externally generated effect onto the measuring chamber plate. If, for example, each of the measuring chambers are only to be half filled, it must be assured that the filled in liquid does not first arrive at the last measuring chamber of the measuring chamber row and entirely fill that chamber which would be the case with an unhindered fluid passage through the capillaries. With the previously described solution, the desired amount arrives first only up to the cross-sectional change. It is then allowed to flow further by the external effect exerted on the measuring chamber plate and so forth until the last chamber has been reached. In this way, the measuring chambers are filled one after the other with the desired amount, without one of these chambers being entirely filled while the others remain empty. One possibility for exerting an effect on the measuring chamber plates in the desired way exists, for example, in that an ultrasonic driver is arranged at the dosing station which is couplable with the measuring chamber plate. By an appropriate ultrasonic impulse, the liquid at the cross-sectional change of a capillary is induced to overcome the xe2x80x9cblockxe2x80x9d and to flow further under the effect of the capillary force.
A measuring chamber plate of the previously described kind can be made in a very simple way in that the measuring chambers and the capillaries are formed by upwardly open recesses in the measuring chamber plates and are subsequently closed by a cover foil. This cover foil is for the optical measurement transparent at least in the area of the measuring chambers.
Also, the measuring chamber plate is advantageously transparent at least in the region of the measuring chamber bottoms and moreover is preferably made of an opaque material to inhibit stray light from one measuring chamber reaching another measuring chamber. A sufficient optical transparency can, therefore, be achieved in that the measuring chamber bottoms have a small thickness in comparison to the thickness of the plate so that the measuring chamber plate is opaque except for at the measuring chamber bottoms.
To inhibit the effect of stray light in the measurement of the measuring chambers and also to enable the use of small or weak light sources, at least one side of each measuring chamber bottom can be formed as a light refracting surface; for example, as a convex lens.
So that the measuring apparatus need not individually sense the measuring chambers of a connected measuring chamber row, it is advantageous if a plurality of pairs of light transmitters/light sensors are provided which pairs in number and arrangement correspond to the measuring chambers of at least one measuring chamber row.
The liquids to be investigated are mostly delivered in cuvettes, which for example are arranged eight at a time in elongated rectangular shaped cuvette holders or racks. The test specimen providing station in accordance with the inventive solution has a cuvette receiving location and a cuvette take-off location in which the cuvette holders are transported perpendicularly to their longitudinal directions, and which locations are connected by a longitudinal conveyor through which the cuvette holders are transported past the dosing station. With the help of the pipetting apparatus, the specimens can be removed from the cuvettes and distributed to the measuring chamber plates. To effect the transfer of the cuvette holders from perpendicular movement to longitudinal movement with the lowest possible technical expense, the inventive solution uses for the longitudinal conveyor an endless conveyor belt which at each end of the longitudinal conveyor is trained over a belt roll and which is receivable in a slot, parallel to the belt direction, in a support surface flush with the transport plane at the cuvette receiving location and the cuvette take-off location, and each of which rolls at a part of its circumferences is flattened along a circular secant. At their flattened regions, the belt rolls do not extend above the support surface so that in the position of a belt roll in which its flattening is located below the underside of the support surface no contact exists between the conveyor belt and the underside of the cuvette holder standing on the support surface. This means that in this position of the belt roll a cuvette holder can be pushed onto and pushed off of the support surface. If the belt roll rotates further, the section of the belt roll having full radius extends through the slot in the support surface so that the conveyor belt comes into contact with the underside of a cuvette holder standing on the support surface and moves the cuvette holder in the longitudinal direction of the conveyor. This solution makes possible, without the use of some type of lifting arrangement and in a very simple way, a transfer of the cuvette holder from perpendicular movement to longitudinal movement.
To assure a sufficient and uniform tensioning of the conveyor belt, the belt rolls at the longitudinal ends of the longitudinal conveyor are so positioned relative to one another on their shafts that the effective length of the conveyor belt in each angular position of the belt rolls is at least nearly constant.
The test specimen providing station serves not only for the delivery of the cuvettes for the removal of the specimens, but also for adjusting the specimens to the given concentrations, which assures uniform test conditions. In connection with this, the cuvette holders have in the inventive solution measuring openings for an optical stretch which extends perpendicular to the longitudinal direction of the holder and to the direction in which the cuvettes are inserted into the holders, with an optical measuring apparatus for measuring the quantity and the absorption capability of the cuvette content being arranged in the area of the longitudinal conveyor. As a rule, the content of the cuvettes is so chosen that the liquid specimens can still be adjusted by thinning with a physiologic table salt solution to the concentration and density desired for the measurement. This adjustment is confirmed with the help of the measuring apparatus. An amount measurement can be carried out in such way that the measuring apparatus has associated with it a lifting mechanism for lifting a cuvette inside of a cuvette holder. By suitable choice of the starting amount of specimen, the optical stretch first runs through the cuvette in air. If the cuvette is then lifted, the measuring beam at some time enters into the liquid, so that the measuring apparatus detects a steplike density change. From the measured lifting path up to this density change, and the known cuvette capacity, the volume of the liquid in the cuvette can be calculated. In connection with the measured density of the liquid, the amount of liquid required for the thinning can then be calculated.
In order in this case to again develop a simple solution, the lifting apparatus is arranged below the upper run of the two-part endless band of the longitudinal conveyor and has a lifting plunger movable into a bottom opening of the cuvette holder in order to lift up the associated cuvette with an upper stop limiting the lifting path. The lifting plunger can at the same time be part of a mixing head for mixing of the content of the cuvette. A suitable mixing head for this can, for example, be an ultrasonic mixer or an HF-mixer. The stop is preferably a spring so that it holds the cuvette in contact with the plunger and at the same time can partake of the induced movements. In this way, the specimen liquid can be mixed quickly with the liquid delivered by means of the pipetting apparatus.